Main drains are a common feature in most water features such as pools, spas, fountains, artificial streams, rivers, ponds, etc. The drain is typically located in the bottom lowest portion of the body or sump that contains the fluid, which in most cases is water.
Such a drain is designed to allow the body of water to be pumped or gravity drained dry, if and when service is required. It is also used to remove fluid from the vessel and transport this fluid to another location for filtering or other uses. In some cases the main drain line is directly connected to the pump suction. In other cases the fluid is transported by natural differential pressure created by a difference in the fluid elevation similar to the way a garden hose is used to drain small pools or bodies of water. In general, all main drains are designed to evacuate the water or fluid from the fluid container. These drains consist of three major parts:
1. The sump which is the water tight housing that makes up the body of the drain.
2. The grating or cover which has a certain amount of open area allowing the water to pass through it into the sump. The function of the grating is to keep large debris from getting caught down in the drain and or plugging up the conduit connected to the drain by the third component called the face piping.
3. The face piping usually consists of a nipple or nipple and flange on larger diameter pipe. Under certain conditions a human body can get caught on the drain and drown.